Project Summary People with sensorineural hearing loss experience difficulties understanding speech in noisy environments, and may have difficulty separating a target voice from among many talkers, and localizing sounds in space. All of these deficits may be attributed to the functional effects of damage to cochlear structures, which include a loss of auditory sensitivity, alterations in loudness perception, and impairments of spectral and temporal processing in the auditory system. In this program of research, behavioral psychoacoustic methodologies and electrophysiological methods are used to study the deficits associated with frequency and time analysis in the impaired cochlea, and the impact of those deficits on the clear understanding of speech and the ability to enjoy music. For the next grant period, the focus of this research will be the study of temporal processing of complex sounds by people with hearing loss. Included are studies of complex pitch produced by harmonic and inharmonic complexes and aperiodic rippled noises, and studies of the ability to perceive the fine structure and envelopes in temporal waveforms. In addition, experiments will include measurement of evoked responses to stimuli with various temporal characteristics. The studies have as their goal the evaluation of the representation of temporal information in the higher auditory centers within the brain, when the inputs to those centers come from an impaired peripheral auditory system. It is hoped that an understanding of the manner in which the temporal information is distorted or lost, as determined by these studies, will help in understanding the functional deficits experienced by hearing-impaired people in their everyday lives.